I recently purchased a 12x18 inch granite surface plate. Herman Stone co. is the maker. Do any of you have any first hand knowledge of a local company that could check the flatness or calibrate it? Basically, trying to find out if it needs to be serviced. It hadn’t been covered for some time but it has cleaned up very nicely. I’d just like to get a sense of it’s general health…
Thanks all.
First: How accurate do you need, e.g. deviation per inch. This will determine if it nees to be reground if out of specification.
Do you know what class of plate it is?
Google Metrology Laboratories in North Texas or DFW.
Just a wild SWAG I can’t imagine it being less $100 to inspect it and give you the inspection diagram. The diagram will be like a contour map of the deviation from a flat plane. The advanatge of this let’s say you need Inspection grade A. 3/4 of the plate may be “A” the rest “B”. They will cert the plate to just “B” but if you know where where the “A” boundary is you can mark on the side of the plate the boundary and if that is acceptably big enough for your item then use that rather than regrind it. No idea the cost of a regrind.
I assume there is no visually apparent chips or damage that need repair.
If you get the plate certified I’m assuming you having the height gauge, indicators, etc. also calibrated, if not, there really isn’t much point in doing the plate if you don’t know the accuracy of tools being used.
Is the plate new when you bought it? There should have been a factory cert that came with it. Unless you are doing work that requires certified inspection equipment (which would mean all measurement tools) that cert should be good for now.
I think autocorrect might’ve gotten you there, presumably you mean ‘metrology’?
David, thank you so much for the info. Here’s a pic of my hunk of granite. I paid a very modest amount so expectations aren’t high. i’m in the process of obtaining guages and such. Surface/height gauge is up next. I mainly wanted to get a sense of whether I need to save and buy a different one or if this will be sufficient for my very limited needs (if you can even call them needs). Frankly, I may be more a bit more in love with the notion of having a decent surface plate than actually needing one. But hey, I have to start somewhere. 
I’m sure if it needs to be reground, I would just buy something new.
Good news is: It’s pink granite, which is considered one of the highest grades of stone.
If the opposite surface is in good shape: no obvious signs of wear, chips, etc. then I’d use it as is unless you really need a super high accuracy surface and have equally high quality certified tools to use on it.
What do you need to inspect that has the need for that kind of accuracy?
Thanks @Kevin. David, I don’t really have any specific need. Was just thinking it might be interesting to know if it was descent or not. But it’s at least a name brand (albeit old) and to your point, at least it’s pink granite. Nothing obviously wrong with it. There’s just one small patch that has some small chipping (isolated to about a 2 sq. inch spot). Here are some additional pics. Clamping ledge on all sides. Forgive the mess.
Thanks again for comments.
If not critical - save the money. If you want to, I’d find a place to resurface it - don;t bother with initial inspection, they’ll inspect after resurface.
To set expectations, a resurface may not get the chips out, or the cracks. It will ensure that reasonable bases on measurement tools as parts will sit consistently on the surface by lapping the plate into one plane. I’m fact, that plate is small enough, that their laps may be larger than it is.
